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Derivative Problems, Please help!

  1. Sep 21, 2004 #1
    Hey, I am having some trouble solving this problem..soon as i see how it works i just know i gunna go "Ooh, thats all i had to do" Here it is:

    A shrinking lollipop. A shperical Tootsie Roll Pop that you are enjoying is giving up volume at a steady rate of 0.08 mL/min. How fast will the radius be decreasing when the Tootsie Roll Pop is 20 mm across?

    Ok, I know I need to take the derivative of V=(4/3)pi(r^3) i just get lost in that proccess...please help..

    THank you very much
  2. jcsd
  3. Sep 21, 2004 #2


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    They are asking you for [tex] \frac{dr}{dt} [/tex]

    Why don't you differiantiate with respect to t?.
  4. Sep 21, 2004 #3


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    Show me your derivative, so i can see where it went wrong.
  5. Sep 21, 2004 #4


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    you need to use the chain rule, dV/dt = (dV/dr) (dr/dt)
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